| 1. |
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| 2. |
- Chen, Junsheng, et al.
(författare)
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Photo-stability of CsPbBr3 perovskite quantum dots for optoelectronic application
- 2016
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Ingår i: SCIENCE CHINA Materials. - : Springer Science and Business Media LLC. - 2095-8226 .- 2199-4501. ; 59:9, s. 719-727
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Tidskriftsartikel (refereegranskat)abstract
- Due to their superior photoluminescence (PL) quantum yield (QY) and tunable optical band gap, all-inorganic CsPbBr3 perovskite quantum dots (QDs) have attracted intensive attention for the application in solar cells, light emitting diodes (LED), photo detectors and laser devices. In this scenario, the stability of such materials becomes a critical factor. We hereby investigated the long-term stability of as-synthesized CsPbBr3 QDs suspended in toluene at various environmental conditions involving the light illumination, atmosphere, and temperature. We found light illumination would induce dramatic degradation of CsPbBr3 QDs reflecting as decreasing absorbance and PL intensity together with red-shifted emission band. Such light instability can be attributed to the photo-induced surface degradation and aggregation. The steady-state spectroscopy, transmission electron microscopy (TEM) and X-ray diffraction (XRD) technics verified that CsPbBr3 QDs trend to aggregate to form larger particles under continuous light soaking. In addition, decreasing PL QY of the QDs during light soaking indicates the formation of trap sites. Such trap sites lead to the red-shifted emission with increasing PL lifetime. Our work reveals that the main origin of instability in CsPbBr3 QDs and provide reference to engineer such QDs towards optimal device application.
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| 3. |
- Geng, Huifang, et al.
(författare)
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Controlled synthesis of highly stable lead-free bismuth halide perovskite nanocrystals : tructures and photophysics
- 2023
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Ingår i: SCIENCE CHINA Materials. - : Springer Science and Business Media LLC. - 2095-8226 .- 2199-4501. ; 66:5, s. 2079-2089
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Tidskriftsartikel (refereegranskat)abstract
- Recently, cesium bismuth halide perovskites have emerged as potential substitutes to their counterparts, cesium lead halide perovskites, owing to their low toxicity. However, the photophysics of cesium-bismuth halides nanocrystals (NCs) have not yet been fully rationalized because their structures remain highly debated. The ultraviolet-visible (UV-vis) absorption along with other photophysical properties such as the nature and lifetime of the excited states vary considerably across the previous reports. Here, we successfully synthesize pure Cs3BiBr6 and Cs3Bi2Br9 NCs via a modified hot-injection method, where the structure can be easily controlled by tuning the reaction temperature. The UV-vis absorption spectrum of the pure Cs3Bi2Br9 NCs features two characteristic peaks originating from the absorption of the first exciton and second exciton, respectively, which ultimately clarifies the debate in the previous reports. Using femtosecond transient absorption spectroscopy, we systematically investigate the excited state dynamics of the Cs3Bi2Br9 NCs and reveal that the photoexcited carriers undergo a self-trapping process within 3 ps after excitation. More intriguingly, the Cs3Bi2Br9 NCs prepared by this method show much better photostability than those prepared by the ligand-assisted reprecipitation process. Photodetectors based on these Cs3Bi2Br9 NCs show a sensitive light response, demonstrating the definite potential for breakthrough optoelectronic applications. [Figure not available: see fulltext.].
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| 4. |
- Huang, Zheng, et al.
(författare)
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Constructing type-II CuInSe2/CuInS2 core/shell quantum dots for high-performance photoelectrochemical cells
- 2024
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Ingår i: SCIENCE CHINA Materials. - 2095-8226. ; 67:1, s. 134-142
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Tidskriftsartikel (refereegranskat)abstract
- CuInSe2 (CISe) quantum dots (QDs) have shown promising applications in photoelectrochemical (PEC) cells due to their nontoxicity, high extinction coefficient, and wide optical absorption range; however, their low PEC performance prevents their applications due to insufficient charge carrier separation and severe charge recombination. Herein, CISe/CuInS2 (CISe/CIS) core/shell structured QDs are designed and constructed to promote charge separation and diminish interface defects. Afterward, the copper vacancy (VCu) state of CISe/CIS QDs is enriched by modulating the precursor molar ratios of In/Cu. Therefore, the radiative recombination of the conduction band edge electrons with the VCu localized holes becomes dominant and prolongs the carrier lifetime compared with intrinsic band-to-band recombination, thus promoting charge separation. Consequently, the VCu-rich CISe/CIS QD-based photoanode shows a high photocurrent density of 8.0 mA cm−2, which is one of the highest values reported for CISe QD-based PEC cells. This work provides an effective approach for promoting charge carrier separation and transfer through surface or intrinsic defect mediation for PEC applications of I–III–VI semiconductor nanocrystals.
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| 5. |
- Li, Guohui, et al.
(författare)
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Efficient heat dissipation perovskite lasers using a high-thermal-conductivity diamond substrate
- 2023
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Ingår i: SCIENCE CHINA Materials. - : Springer Science and Business Media LLC. - 2095-8226 .- 2199-4501. ; 66:6, s. 2400-2407
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Tidskriftsartikel (refereegranskat)abstract
- Efficient heat dissipation that can minimize temperature increases in device is critical in realizing electrical injection lasers. High-thermal-conductivity diamonds are promising for overcoming heat dissipation limitations for perovskite lasers. In this study, we demonstrate a perovskite nanoplatelet laser on a diamond substrate that can efficiently dissipate heat generated during optical pumping. Tight optical confinement is also realized by introducing a thin SiO2 gap layer between nanoplatelets and the diamond substrate. The demonstrated laser features a Q factor of ∼1962, a lasing threshold of 52.19 µJ cm−2, and a low pump-density-dependent temperature sensitivity (∼0.56 ± 0.01 K cm2 µJ−1) through the incorporation of the diamond substrate. We believe our study could inspire the development of electrically driven perovskite lasers. [Figure not available: see fulltext.].
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| 6. |
- Li, Yihang, et al.
(författare)
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Efficient reversible CO/CO2 conversion in solid oxide cells with a phase-transformed fuel electrode
- 2021
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Ingår i: SCIENCE CHINA Materials. - : Springer Science and Business Media LLC. - 2095-8226 .- 2199-4501. ; 64:5, s. 1114-1126
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Tidskriftsartikel (refereegranskat)abstract
- The reversible solid oxide cell (RSOC) is an attractive technology to mutually convert power and chemicals at elevated temperatures. However, its development has been hindered mainly due to the absence of a highly active and durable fuel electrode. Here, we report a phase-transformed CoFe-Sr3Fe1.25Mo0.75O7−δ (CoFe-SFM) fuel electrode consisting of CoFe nanoparticles and Ruddlesden-Popper-layered Sr3Fe1.25Mo0.75O7−δ (SFM) from a Sr2Fe7/6Mo0.5Co1/3O6−δ (SFMCo) perovskite oxide after annealing in hydrogen and apply it to reversible CO/CO2 conversion in RSOC. The CoFe-SFM fuel electrode shows improved catalytic activity by accelerating oxygen diffusion and surface kinetics towards the CO/CO2 conversion as demonstrated by the distribution of relaxation time (DRT) study and equivalent circuit model fitting analysis. Furthermore, an electrolyte-supported single cell is evaluated in the 2:1 CO-CO2 atmosphere at 800°C, which shows a peak power density of 259 mW cm−2 for CO oxidation and a current density of −0.453 A cm−2 at 1.3 V for CO2 reduction, which correspond to 3.079 and 3.155 mL min−1 cm−2 for the CO and CO2 conversion rates, respectively. More importantly, the reversible conversion is successfully demonstrated over 20 cyclic electrolysis and fuel cell switching test modes at 1.3 and 0.6 V. This work provides a useful guideline for designing a fuel electrode through a surface/interface exsolution process for RSOC towards efficient CO-CO2 reversible conversion.
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| 7. |
- Liao, Xiaoqi, et al.
(författare)
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Large exchange bias in magnetic shape memory alloys by tuning magnetic ground state and magnetic-field history
- 2020
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Ingår i: Science China.Materials. - : Springer Nature. - 2095-8226 .- 2199-4501. ; 63:7, s. 1291-1299
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Tidskriftsartikel (refereegranskat)abstract
- The exchange bias is of technological significance in magnetic recording and spintronic devices. Pursuing a large bias field is a long-term goal for the research field of magnetic shape memory alloys. In this work, a large bias field of 0.53 T is achieved in the Ni50Mn34In16-xFex (x = 1, 3, 5) system by tuning the magnetic ground state (determined by the composition x) and the magnetic-field history (determined by the magnetic field H-FC during field cooling and the maximum field H-Max during isothermal magnetization). The maximum volume fraction of the interfaces between the ferromagnetic clusters and antiferromagnetic matrix and the strong interfacial interaction are achieved by tuning the magnetic ground state and the magnetic-field history, which results in strong magnetic unidirectional anisotropy and the large exchange bias. Moreover, two guidelines were proposed to obtain the large bias field. Firstly, the composition with a magnetic ground state consisting of the dilute spin glass and the strong antiferromagnetic matrix is preferred to obtain a large bias field; secondly, tuning the magnetic-field history by enhancing H-FC and reducing H-Max is beneficial to achieving large exchange bias. Our work provides an effective way for designing magnetically inhomogeneous compounds with large exchange bias.
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| 8. |
- Liao, Xiaoqi, et al.
(författare)
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Low-field-induced spin-glass behavior and controllable anisotropy in nanoparticle assemblies at a liquid-air interface
- 2022
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Ingår i: SCIENCE CHINA-MATERIALS. - : Springer Nature. - 2095-8226 .- 2199-4501. ; 65:1, s. 193-200
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Tidskriftsartikel (refereegranskat)abstract
- Stacking nanoscale-building blocks into one-dimensional (1D) assemblies with collective physical properties is a frontier in designing materials. However, the formation of 1D arrays using weak magnetic fields and an in-depth understanding of their magnetic properties remain challenging. Here, low-dimensional assemblies of iron oxide nanocubes with a disordered arrangement are fabricated at the diethylene-glycol/air interface in the presence of assembly fields (0/1/3/5/30/50 mT). Ring-shaped assemblies gradually transform as the assembly field increases from 0 to 50 mT, first to a porous network consisting of elongated assemblies and then to an aligned array of filaments, in which the aligned filaments are formed when the assembly field is >= 3 mT and duration t > 14 min. Spin-glass characteristics and static (dynamic) anisotropy factors similar to 2(3) are achieved by tuning the strength of the assembly field. In the presence of a relatively weak assembly field, the interplay between dipolar interactions and disorder with respect to magnetic easy axis alignment leads to spin-glass characteristics. The alignment of the magnetic easy axes and the strength of the dipolar interactions increase with increasing assembly field, resulting in the disappearance of spin-glass characteristics and enhancement of the magnetic anisotropy. This study presents a strategy for obtaining magnetic assemblies with spin-glass behavior and controllable anisotropy while shedding light on the magnetic interactions of low-dimensional assemblies.
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| 9. |
- Liu, Yang, et al.
(författare)
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Inorganic ligands-mediated hole attraction and surface structuralreorganization in InP/ZnS QD photocatalysts studied via ultrafast visibleand midinfrared spectroscopies
- 2022
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Ingår i: SCIENCE CHINA Materials. - : Springer Science and Business Media LLC. - 2095-8226 .- 2199-4501. ; 65:9, s. 2529-2539
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Tidskriftsartikel (refereegranskat)abstract
- Photoinduced carrier dynamical processes dominate the optical excitation properties of photocatalysts and further determine the photocatalytic performance. In addition, as the electrons generally possess a faster transfer rate than holes, hole transfer and accumulation are critical, and they play the key efficiency-limiting step during the photocatalytic process. Therefore, a comprehensive understanding of the dynamics of photogenerated holes and their determining factors in the photocatalytic system is highly essential to rationalize the full catalytic mechanism and develop highly efficient photocatalysts, which have not yet been revealed. In this work, the photoinduced charge carrier dynamics in InP/ZnS quantum dots (QDs) capped with long-chain L-typed ligands (oleylamine) and inorganic ligands (sulfide ion (S2−)) were explored. Time-resolved photoluminescence and femtosecond transient-absorption spectroscopy unambiguously confirmed the ultrafast hole transfer from the InP core to S2− ligands. Moreover, by probing the bleach of vibrational stretching of the ligands with transient midinfrared absorption spectroscopy, the hole transfer time was determined to be 4.2 ps. The injected holes are long-lived at the S2− ligands (>4.5 ns), and they can remove electrostatically attached surfactants to compensate for the spatial charge redistribution. Finally, compared with other inorganic ligands such as Cl− and PO43−, S2− balances the ionic radii and net charge to ensure the optimal condition for charge transfer. Such observation rationalizes the excellent photocatalytic H2 evolution (213.6 µmol mg−1 within 10 h) in InP/ZnS QDs capped with S2− compared with those capped with other ligands and elucidates the role of surface ligands in the photocatalytic activity of colloidal QDs.
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| 10. |
- Liu, Yangyang, et al.
(författare)
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Stable Li metal anode by crystallographically oriented plating through in-situ surface doping
- 2020
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Ingår i: Science China Materials. - : Springer Science and Business Media LLC. - 2199-4501 .- 2095-8226. ; 63:6, s. 1036-1045
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Tidskriftsartikel (refereegranskat)abstract
- Lithium (Li) metal is regarded as the holy grail anode material for high-energy-density batteries owing to its ultrahigh theoretical specific capacity. However, its practical application is severely hindered by the high reactivity of metallic Li against the commonly used electrolytes and uncontrolled growth of mossy/dendritic Li. Different from widely-used approaches of optimization of the electrolyte and/or interfacial engineering, here, we report a strategy of in-situ cerium (Ce) doping of Li metal to promote the preferential plating along the [200] direction and remarkably decreased surface energy of metallic Li. The in-situ Ce-doped Li shows a significantly reduced reactivity towards a standard electrolyte and, uniform and dendrite-free morphology after plating/stripping, as demonstrated by spectroscopic, morphological and electrochemical characterizations. In symmetric half cells, the in-situ Ce-doped Li shows a low corrosion current density against the electrolyte and drastically improved cycling even at a lean electrolyte condition. Furthermore, we show that the stable Li LiCoO2 full cells with improved coulombic efficiency and cycle life are also achieved using the Ce-doped Li metal anode. This work provides an inspiring approach to bring Li metal towards practical application in high energy-density batteries.
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